This NIH Challenge Grant application addresses the specific Challenge Area (05): Comparative Effectiveness Research, and the specific Challenge Topic, 05-CA-104: Comparative Effectiveness Research in Cancer Treatment. This study will examine patterns of treatment with erythropoietic stimulating agents (ESA) in patients with myelodysplastic syndromes (MDS), and compare clinical benefits, risks, and costs associated with any ESA use, and different levels of ESA exposure. The alternative for low-risk patients with MDS associated anemia is supportive care with red blood cell transfusions and management of iron overload. ESAs have been used for the treatment of anemia in MDS patients for approximately 15 years, with a 20 - 40% response rate and median response duration of two years. High-risk MDS patients and those with poor or lapsed response to ESAs may receive 5 azacitidine or decitabine. Clinicians treating MDS patients have widely adopted ESA use for anemic MDS patients despite the lack of large-scale clinical trial evidence demonstrating longer-term clinical benefits. In 2007 the Food and Drug Administration administered a warning concerning the use of ESAs in patients with cancer related anemia due to apparent increase in thromboembolic events, as well as a possible decrease in relapse-free survival. The absence of large scale randomized trials in MDS precludes definitive conclusions regarding the safety and efficacy of these agents in this population;clinical trials randomizing between ESAs and supportive care would be of limited feasibility in the US. The recent inclusion of MDS as a reportable diagnosis in the SEER database (2001) provides an opportunity to explore the current use of ESAs in MDS patients in the Medicare population. By examining claims data linked to SEER reported MDS diagnoses, the patterns of ESA use in the Medicare population will be described. We will examine the association between ESA use and health outcomes including thromboembolic events, disease progression to AML, and overall survival. SEER-Medicare cases will also be compared to the survival of patients from an historic cohort of untreated patients (International MDS Risk Analysis Workshop (IMRAW) data base) to further estimate the effect of ESA exposure on health outcomes. The effect of ESA use on cost of care will also be examined. Finally, we will use a separate dataset that captures Medicare enrollment and claims data, including Medicare Part D (prescription drug) claims for MDS patients from 2005 through 2008. We will use these data to examine whether patterns of ESA use, transfusions, and other drug therapies have been affected by availability of a new oral agent (lenalidomide) starting in 2006, and the effect of the FDA and CMS regulatory activities, which occurred in 2007. These results will have important treatment and policy implications regarding the relative safety and efficacy of ESAs in this elderly MDS patient population and may inform future CMS coverage decisions. Myelodysplastic syndromes (MDS) are the most common hematologic malignancy in the elderly, with at least 10,000 new cases diagnosed each year. Erythropoietic stimulating agents (ESA) are effective in treating the symptomatic anemia that affects MDS patients, but little is known about longer term positive and negative health effects of ESAs, compared to supportive care with repeated blood transfusions. In this study, we will use data from regional cancer registries that is linked to Medicare enrollment and insurance claims data. We will examine the characteristics of Medicare beneficiaries with MDS, patterns of treatment, safety and effectiveness of ESA use, and costs of care.